CELL

 

All living things are made up of cells. They are the basic structural and functional units of life. Robert Hooke discovered the cell in 1665. The average size of a cell varies between 10 micrometers (µm) to 150 micrometers (µm).

  • The simplest living organisms are made up of one cell only. These organisms are described as UNICELLULAR organisms.  E.g. Bacteria
  • Most other living organisms have many cells and are described as MULTICELLULAR organisms. E.g. Birds

A cell is a very small piece of transparent jelly-like substance, surrounded by a thin covering. The jelly is called the cytoplasm.  The covering is called the cell membrane. Most of the cells also have dark area inside the cell called a nucleus

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MESENTERY A new organ in Human

 

New organ discovered inside human body by scientists

 

A new organ called mesentery has been discovered inside the human body.

It was previously thought to be just a few fragmented structures in the digestive system. The scientists have realized it is in fact one, continuous organ. Now we have 79 organs in our body.

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HUMAN DIGESTIVE SYSTEM

The digestive system also known as the alimentary canal or gut is a long tube running from the mouth to the anus, with associated organs together with a number of associated glands that help in digestion. The human digestive system is well adapted for digestion and absorption.

Digestion is the process by which insoluble, in diffusible form of food is converted into soluble,diffusible form form so that the food can be absorbed into the blood

There are five processes in digestion

  1. Ingestion
  2. Digestion
    • Mechanical digestion
    • Chemical digestion
  3. Absorption
  4. Assimilation
  5. Egestion
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DIFFUSION, OSMOSIS,AND ACTIVE TRANSPORT

DIFFUSION
Diffusion is the movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient until evenly distributed.Concentration gradient: the difference in concentration between two regions.
Why does diffusion occur?
1. There is a great deal of empty space between molecules of all substances. (The spaces are more in gases, less in liquids, and least in solids).
2. As all the molecules are always in a constant random motion they collide all the time.

What are the factors affecting rate of diffusion?
1. Thickness of membrane: the thinner the cell membrane, the faster the diffusion.

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AIR POLLUTION BY GREEN HOUSE GASES (CARBON DIOXIDE AND METHANE) CONTRIBUTING TO GLOBAL WARMING.

GLOBAL WARMING
The atmosphere is trapping too much heat and causing the earth to heat up. This is known as GLOBAL WARMING.
GREEN HOUSE GASES
Carbon dioxide , Methane ,Nitrous oxide ,CFCs etc are called ‘green house gases’. These gases form a layer in the atmosphere and this layer acts like glass in the ‘green house’. Most of the light energy from the sun is emitted in short wave lengths, and it can pass through the layer of green house gases. The sun light warms the ground and the warm ground sends out radiation with longer wave lengths which cannot pass out through the layer of Carbon dioxide  .So in effect, Carbon dioxide  lets the light energy in, but doesn’t let all the heat energy out. So heat is trapped in the atmosphere as in a green house.

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EFFECT OF HUMAN ACTIVITY ON ECOSYSTEM

Pollution
Learning Objectives
Describe the effects of man on the ecosystem with emphasis on the examples of international importance (Tropical rain forest, oceans, and important rivers)
Describe the consequences of deforestation in terms of soil stability, climates and local human population.
Evaluate the effects of:
Water pollution by sewage, by inorganic waste and nitrogen containing fertilizers.
Air pollution by Sulphur dioxide and oxides of nitrogen (acid rain)
Pollution due to insecticides.

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SUPPORT, MOVEMENT & LOCOMOTION

elbow joint 4
Support: refers to the skeleton and its role in holding up the body structure and giving shape.
Movement: refers to the change in the position of one part of the body in relation to another part.
Locomotion: refers to the movement of the entire body from one place to another.
Humans and all other vertebrates have skeletons based on the following plan. The skull, backbone (vertebral column) and rib cage form the main axis of the body and so are called axial skeleton. The shoulder blades, hips and the arm and leg bones are attached (appended) to the axial bones and so are called the appendicular skeleton.
The bone contains 50% water and 50% solid matter. The solid matter consists of 57% calcium carbonate and calcium phosphate and 33% organic matter
FUNCTIONS OF BONES

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USE AND ABUSE OF DRUGS

 

Definition:- a drug is an externally administered substance which modifies or affects chemical reactions in the body.

Beneficial effects of drugs

  1. For pain relief – drugs like aspirin, paracetamol and morphine.
  2. For treatment of diseases – diseases caused by bacteria, such as syphilis are treated with drugs called Antibiotics. A well-known antibiotic is penicillin.
  3.  For its mood influencing effect. – Useful for treating patients with emotional disorders such as depression.
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CONSERVATION OF NATURAL RESOURCES

Man by his intelligence uses every possible way to alter the balance of the nature to satisfy his selfish motives. There are about 10 million different species of organisms in the biosphere. At present, because of human activities, the world may be losing up three species a day, and the rate is increasing, so inevitably some species are being lost before we even know they exist. Then they become extinct for ever; because it is not simply death –it is an end to birth. So it is a must to conserve the species.

Conservation can be described as an attempt by man to develop a way of life that does not disturb the balance of nature, and yet allows him to maintain all the advantages of modern civilization.

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